Aerobatics is the practice of flying maneuvers involving aircraft attitudes that are not used in normal flight. Aerobatic flying requires a broader set of piloting skills and exposes the aircraft to greater structural stress than for normal flight. Most aerobatic maneuvers involve rotation of the aircraft about its longitudinal (roll) axis or lateral (pitch) axis. Other maneuvers, such as a spin, displace the aircraft about its vertical (yaw) axis. Maneuvers are often combined to form a complete aerobatic sequence for entertainment or competition.